iot_presign.js

var presignIOTMQTTConnection  = function(endpoint, credentials) {
	//Turn off param validation because of the hackery coming up
	var service = new AWS.IotData({endpoint : endpoint, credentials : credentials, paramValidation: false});

	//MQTT broker uses a different servicename in the sigv4 algo
	service.api.signingName = "iotdevicegateway";

	//1. Create a request object for another, sorta similar request
	//2. Save off our session token and delete it from the credentials(so it doesn't get signed)
	//3. Register to an event in the state machine to adjust the path
	//4. Sign it!
	//5. Restore session token, and add it to the url
	var req = service.getThingShadow({});
	var sessionToken = service.config.credentials.sessionToken;
	delete req.service.config.credentials.sessionToken;
	req.on("afterBuild", function(data){ data.httpRequest.path = "/mqtt"; });
	var url = req.presign().replace("https:", "wss:");
	req.service.config.credentials.sessionToken = sessionToken;
	url += "&X-Amz-Security-Token=" + encodeURIComponent(credentials.sessionToken);
	return url;
};